The prior art in the attempt to develop a device to protect care-givers from needle sticks includes U.S. Pat. No. 4,170,993 to Alvarez, which describes a sliding intravenous needle carrier assembly. This patent covers a different application than the present invention.
U.S. Pat. No. 4,425,120 to Sampson, U.S. Pat. No. 4,702,738 to Spencer, U.S. Pat. No. 4,723,943 to Spencer, and U.S. Pat. No. 4,693,708 to Wanderer all show needle protection systems. In each of these cases, the needle protection cover is designed to cover the syringe body. This increases the size of the syringe body and may cover or obscure the measurement graduations printed on the side of the syringe. Also in each of these cases, the syringe body must be modified to make the syringe cover function as intended. Standard syringes are not usable with these devices.
U.S. Pat. No. 4,966,592 to Burns is similar to the Sampson, Spencer '738, and Spencer '943 patents, in that the needle protection cover passes over the syringe barrel with the same disadvantages noted. It is different than the previous three patents in that it uses a spring to activate the needle cover and has an override feature. It has two major disadvantages. The first is that the device relies on the friction fit of a collar to hold the needle protection system in place on the syringe. The system can slip off and render the syringe unsafe. The second major disadvantage is that the pin that controls the device's operation passes through an open slot, so that the operator or a foreign object may interfere with the function of the safety system by obstructing the slot during operation.
The Jennings U.S. Pat. No. 4,693,708 shows a blood sampling system which has a needle cover that slides over the outside of a piston sleeve to cover the needle after the sample has been taken. The needle cover is manually operated and must be fully extended before the unit is completely safe.
U.S. Pat. No. 4,695,274 issued to Fox shows a needle hub with a protective cover mounted on a syringe. This device must be manually activated to uncover the needle for use. After use, the operator must manually push the outer cover to its locked position. Two embodiments of this device are shown. One embodiment has an external slot where the operator's hand or a foreign object can obstruct the safe operation of the device. In the other embodiment, the needle cover slides over the syringe barrel, thereby obstructing the graduations appearing on the barrel.
U.S. Pat. No. 4,804,371 to Vaillancourt shows a completely different concept, where the needle cover mounts on the hub of a needle which in turn is attached directly to a syringe. This device has a spring to push a small cap over the end of the exposed needle. This design does not lock in the safe position, and the needle cover is really only a guide to allow the operator to reinstall the original needle cap.